THE ROOTS AND GANGLION OF THE TRIGEMINUS. I33 



II. — The Roots and Ganglion of the Trigeminus. 



The sensory and motor roots of the trigeminus issue 

 high up on the side of the oblongata and so intimately- 

 fused that their separation is not easy, even microscopi- 

 cally (Figs. 4, 12, 20-23). 



I. — The Motor Root. 



The motor nucleus of the trigeminus lies in the floor of 

 the ventricle laterally of the fasciculus longitudinalis dor- 

 salis and somewhat removed from it. Both the motor 

 nucleus and root lie farther dorsally than the spinal V 

 tract and at their exit the motor fibres are dorsal, a rela- 

 tion, however, which is not maintained peripherally. A 

 broad band of fibres arising apparently in the motor 

 nucleus of the opposite side passes through the nucleus and 

 doubtless contributes to the root. It also passes through 

 the fasciculus longitudinalis dorsalis and may derive some 

 fibres from that source. 



The motor root passes through and mingles with the 

 general cutaneous root so intimately that it is difficult for 

 a short distance from their exit to distinguish them. 

 Doubtless fibres from other than the motor nucleus, the 

 sensory nucleus and the spinal V tract enter the V nerve, 

 but as they cannot be separately followed peripherally, I 

 have devoted no especial attention to them. Though the 

 general cutaneous and motor fibres cannot be clearly sepa- 

 rated for a short distance after their exits, they can be 

 separated both centrally and peripherally of this point, so 

 that their entire courses can be given with all needful 

 accuracy. In the case of none of the other components 

 which participate in the V + VII ganglionic complex is 

 there any difficulty in distinguishing them and following 

 them throughout the complex. 



